Igniting an oil stratum for in situ combustion



M. SANTOURIAN IGN ITING AN OIL STRATUM FOR IN SITU COMBUSTI ON Filed Dec.

TEMPERATURE REcoRDER Dec. 26, 1967 M w a a. l|1r|| v |1 8 4 d n HHHH c l I I ||l l v m F b 6 M 2 3 v ML "IN I V. N m 4 United States Patent 3,360,041 IGNITING AN OIL STRATUM FOR IN SITU COMBUSTION Melcon Santourian, Mashed, Iran, assignor to Phillips Petroleum Company, a corporation of Delaware Filed Dec. 20, 1965, Ser. No. 515,141 9 Claims. (Cl. 166-2) This invention relates to a process or technique for igniting a permeable oil stratum for initiating in situ c mbustion therein.

Production of oil from oil strata by both reverse and direct drive in situ combustion has come into use in the petroleum industry. One of the problems encountered in in situ combustion within an oil stratum is that of initiating combustion which can be sustained by an air drive. A desirable procedure in igniting an oil stratum around a production well offset from an injection well wherein reverse drive of the combustion zone from the production well to the injection Well is to be used comprises heating the production well bore to at least ignition temperature and feeding air or other O -containing, combustion-supporting gas thru the injection well and forcing same to the hot area at the production well. This technique is not always successful and various methods have been proposed for assisting in establishing a sustainable combustion zone moving toward the injection well. One procedure which has been proposed is to inject into the annulus surrounding the production well a low ignition point liquid fuel which ignites spontaneously when contacted with air, particularly, under high pressure. This procedure is designed to establish a combustion zone extending radially from the production well, but this does not always operate as expected because the injected air tends to drive the injected fluid (in the annulus surrounding the production well) into the production well without burning any substantial quantity thereof in the stratum surrounding the production well. Thus, frequently, the intended ignition does not take off to establish an inverse drive in situ combustion process.

The present invention is concerned with a process or technique of operation for initiating an inverse burning combustion front in an oil stratum.

Accordingly, it is an object of the invention to provide a process for igniting an oil stratum around a production well and establishing a combustion zone which can be maintained by inverse drive of air or other oxidizing gas. Another object is to provide a process for initiating an inverse burning combustion zone around a central well flanked on either side by offset injection Wells. It is also an object of the invention to provide a process for establishing an inverse burning combustion front around a production well, utilizing a spontaneously ignitable, lowignition point liquid fuel, which does not drive the fuel into the production well. Other objects of the invention will become apparent to one skilled in the art upon consideration of the accompanying disclosure.

A broad aspect of the invention comprises depositing a spontaneously ignitable, low-ignition point liquid fuel in an annulus adjacent a central production or ignition well located between two offset injection wells, thereafter shutting-in the central well and injecting air or other combustion supporting, O -containing gas thru one of the injection wells while producing thru the other so that the injected gas passes into the annulus containing fuel and spontaneously ignites same, injection being continued to establish a substantial combustion zone and ignite the inplace oil, thereafter opening the central well to flow and injecting combustion-supporting gas thru the other injection well so as to initiate combustion in the injected fuel nearest the second injection well and move the resulting 3,360,041 Patented Dec. 26, 1967 ICC combustion zone toward the second injection well. Production from both combustion zones is recovered thru the central well which becomes the production well for the following inverse burning drive thru the stratum intermediate the production and injection wells. It is feasible to utilize a ring pattern of wells around a central well or a line of production wells intermediate parallel lines of injection wells. The ring pattern is operated by utilizing substantially diametrically opposite ring wells as initial injection wells to establish the combustion zones on opposite sides of the production well and thereafter injecting thru all of the ring wells whereby the burning Zone is moved toward the other injection wells (not used in the original ignition).

Another embodiment of the invention comprises first packing off the central well just below the upper level and also just above the lower level of the stratum in conventional manner around a tubing string and then forcing a liquid solvent for the in-place oil thru the annulus surrounding the central well either from above the upper packer to below the lower packer or vice verse, this being controlled by injecting either thru the annulus or thru the tubing string and producing thru the other flow path. After a substantial annulus has been at least substantially depleted of in-place oil, the selected spontaneously ignitable liquid fuel is injected so as to displace the solvent in the annulus around the central well and deposit in said annulus sufficient fuel to initiate combustion of the in place oil. After the selected fuel has been deposited in the annulus, operation is conducted as above described, first closing the central well and injecting thru one of the offset wells until a substantial combustion zone has been established and then opening the central well to flow and injecting thru the other offset well also so as to establish another combustion zone in the annulus nearest the second offset well. This technique is useful in strata containing rather heavy viscous oil and assures deposition in the annulus around the central well of sufiicient fuel to initiate a combustion zone sustainable by inverse air injection from the offset wells.

A preferred gaseous oxidant is air because of the economics involved but other gaseous oxidants may be utilized such as O -enriched air, substantially pure ozone, gaseous nitrogen oxides, and gases containing combustionsupporting concentrations of these oxidants as well as mixtures of such gases.

Preferred spontaneously ignitable fuels include tung oil and linseed oil. However, other low-ignition point liquids are also suitable for the combustion fuel, such as unsaturated aliphatic hydrocarbons including cracked distillates, cyclic hydrocarbons such as turpentine, tetralin, or decalin, unsaturated aliphatic or cyclic O -containing compounds such as crotin-aldehyde, allyl alcohol, furfural, and aliphatic cyclic nitrogen-containing compounds such as ethylenediamine, or aniline or phenylhydrazine. Mixtures of these fuels may also be utilized and the fuel may include an oxidation catalyst such as cobalt naphthenate, manganese resinate and similar well-known oxidation catalysts which do not plug the stratum. Minor amounts of catalyst such as in the range of 0.05 to 1 weight percent of the injected fuel, are used in the operation.

The invention is not limited to the particular fuel or catalyst or oxidant utilized, but resides in the specific manner of operating with these materials. Hence any of the materials available which function in the intended manner are within the scope of the invention.

A more complete understanding of the invention may be had by reference to the accompanying schematic drawing of which FIGURE 1 is a fragmentary elevation in partial section thru a central well and a pair of offset injection wells penetrating an oil stratum and FIGURE 2 is a plan view of laboratory apparatus in which in situ combustion runs were made.

Referring to FIGURE 1 an oil stratum 111 is penetrated by a central well 12 and oifset injection Wells 14 and 16.

series of in-line production wells 12 and inject air thru offset parallel lines of injection wells 14 and 16.

The invention has been demonstrated in the laboratory utilizing a 30" long, 2%" diameter stainless steel tube The wells may either be cased thru the oil stratum or in 5 packed with Ottawa sand containing 1350 barrels per acre a consolidated sand open hole may be used for the comfoot of Morichal Group II oil. The tube was well inbustion process. An annulus 18 surrounding well 12 is sulated and equipped with 4 sectional heaters and thersubstantially saturated with a selected spontaneously ignitmocouples to provide an essentially adiabatic tube. Eight able fuel by injecting same thru well 12 in obvious manner. thermocouple leads connected to an 8-point Brown re- In Operation with the arrangement of FIGURE 1 it is 10 corder provided absolute temperature measurements durpreferred to first inject air or other gaseous oxidant thru mg In em] eembustlon e- Addmenal, 4 h PP well 12 into the surrounding stratum until breakthru of leads were used to mammm a near'adlabatle eonemen air occurs thru wells 14 and 16. This substantially satuthe tube l times, using 4 commerciall available rates the stratum with O and hastens the ignition process Aeremag differential tempeljatllre eontmilers The when injecting air thru 1115 injection wells. After the 15 p u described and e 18 lllustrateq 1n FIGURE 2 preliminary air injection is terminated at breakthru, the Wherem numeral 30 eeslgnates stalpless steel tube selected oxidizable liquid fuel is injected thru well 12 so havmg 8 thermocouples heatmg eeetlens as to substantially saturate an annulus surrounding this and Separated y dotted hues Lmes and 43 e well. The amount of injected fuel depends upon the char- Provlded at epposlte e 9 tube 30 for flew of flutes acter of the stratum as to porosity, oil saturation, il 20 Y e from the e with! tube A pelferated "3- characteristics, thickness of the stratum, etc. Ordinarily, Jeetlon and Produce? eendult 44 extended l a substantial slug of the spontaneously ignitable fuel is send ee the Imdseeuen of e tube 30 for mlectlon injectad so as to saturate an annulus from to Swami of oxidizable fuel and for production of produced fluids. feet thick immediately surrounding well 12. Following Thermocouples 32 were eenneetee l a temperature the deposition of fuel in annulus 18, well 12 is shut-in corder 9 Acmmagile m dlfierenual temperature and air is injected either thru We 14 or well 16, the controller un1t50 were utilized to maintain near-adiabatic one not bfiing used for injection bang utilized as a conditions in the tube at all times. TheAcromags control duction well. Assuming that air is injected thru well 14 the amount of heating m the four heatlng 'Sectlens with well 12 shut-in, the injected air and/ or air already e deposited in the stratum passes into the annulus 18 con- Uhhlihg the apparatus of FIGURE 2, Packfid with taining the injected spontaneously ignitable fuel and inititflWa Sand and Containing Morichal Group H on ates combustion thereof. Continued supplying of air thru scribed thfi h Was preheated to to this annulus and the fuel therein expands the combustion rhspohd to the Morlchal field fesefvoil' temperaturezone, raises the temperature in the annulus to the ignition Thfireaflel" a Slug of Catalyzed lung Oil (chhtaihihg ()1 temperature of the in-place oil, thereby igniting same and 'f P of cobalt haphthehath) was ihlhcted thru causing the resulting combustion zone to move inversely conduit 4 4 so as to saturate a substantial annulus of the to the fl f i toward 14. wh a b i l surroundmg sand with the fuel. Tube 44 was then closed combustion zone has been established, well 12 is open slmulahhg f Shut-in Was then inlehted thru 1111c to flow while continuing injection of air thru well 14 and 40 Whfle e was open to flow iron} the sane- An air is also new injected thru Well 16 which has prior to air fiux density of about 150 standard cubic feet per hour this point been utilized as a production well. Air injected Square foot of erose Semen of sand was ethru well 16 arrives at the annulus around well 12 con- Thls Phase of the Operation was eentmeed and Periodle taining the injected fuel and initi te a Combustion Zone temperature measurements recorded until the temperature in the area of 20 in the Same manner as Occurmd on the profile thru the tube, as a result of the oxidation reaction, opposite side of we 12 from air injected thm Well 14' indicated the 1n1t1at1on of a counterflow combustion from Here again, a reverse or inverse burning combustion zone about the e h 9 011 Heated (amend f 44) moves away from the central production well toward the g g an g i i 2 9? l injection well. During the movement of the combustion n P 0 6 Opera} on was ar e y mlecimg zones toward the in.ection Wells on rind an a air thru line 43 and opening condult 44 to production. f d ad e overedthr p y m 1 This phase of the operation was continued until the temv ah e e I e f u 1 We perature profiles indicates the initiation of the second eh i 12mg 3 ring Pattern e Wel 8 around a Central counterflow or inverse combustion. This second reverse W l, the flhg wens and 16 e used as combustion zone moved from adjacent conduit 44 toward ect1on wells after establishing of combustion zone 20, i i j i 11 43 thereby advancing the combustion zones 18 and 21) toward The table below presents data representing the temthe other in ection wells, also. It1s feasible to initiate comperature profile in the tube obtained during the life of bustion 1n the manner of the invention around each of a the run or test.

TABLE Time T1 T2 T3 T1 T5 T5 T7 T5 Flux TABLEOontinued Time T T: T3 T4 T5 T T7 T Flux Norm-At 3:35 injection at both ends was commenced with production thru center.

The invention avoids producing the spontaneously ignitable fuel back into the well thru which it was injected and thus conserves this relatively expensive fuel and avoids burning the same in the production wellbore. It

also assures suflicient fuel in the annulus surrounding the production well for ignition of a sustainable counterflow combustion zone.

In some instances, it is desirable to establish adequate gas permeability around the production well by injecting inert gas following the slug of fuel so that air from the injection wells does not bypass the slug and flow around it. After the slug has been dispersed by an inert gas, it may be desirable to fill up the wellbore with water or some other liquid in order to minimize hold up of mobil slug material as it is moved about in the formation by the flowing air. This movement of slug with air movement is actually a favorable phenomenon in this process because it increases the slug saturation per unit volume of stratum and thus assures a favorable condition for reaction to take place.

When the oil surrounding the central production well is highly viscous, it is desirable to flush out the annulus into which the fuel is to be injected so as to provide a void space necessary for containment of the injected fuel. As disclosed above, the annulus is packed off just below and just above the boundaries of the stratum in conventional manner and a solvent for the in-place crude oil such as light oils, kerosene, benzene, etc. is forced thru such as light oils, kerosene, benzene, etc. is forced through to deposition of the low ignition point fuel in the annulus. During this process, if the sand is unconsolidated, the sand grains are free to move and shift from one location to another and consequently compensate for any high permeability streaks or inhomogeneities that naturally exist around the well, which assures more uniform combustion in the annulus when the air supply contacts the oxidizable fuel.

Certain modifications of the invention will become apparent to those skilled in the art and the illustrative details disclosed are not to be construed as imposing unnecessary limitations on the invention.

I claim:

1. A process for initiating in situ combustion in a permeable oil stratum penetrated by a central well and first and second wells offset in substantially opposite directions from said central well, which comprises the steps of:

(l) injecting thru said central well a combustionsupporting volume of a low-temperature oxidizable liquid into an annulus of said stratum adjacent said central well;

(2) thereafter, shutting in said central well and injecting gaseous O -containing oxidant thru said first Well so as to contact said liquid therewith and ignite and burn same, thereby igniting in-place oil adjacent said annulus and establishing a combustion zone;

(3) continuing the injecting in Step 2 so as to cause said combustion zone to move toward said first well;

(4) during Steps 2 and 3, producing thru said second well;

(5) thereafter, opening said central well to production and injecting gaseous O -containing oxidant thru said second well, contacting the oxidizable liquid in said annulus nearest said second well therewith, and burning said liquid thereby igniting in-place oil and establishing a second combustion zone; and

(6) continuing the injecting in Step 5 so as to move said second combustion zone toward said second well while producing fluids from both combustion zones thru said central well.

2. The process of claim 1 wherein said oxidizable liquid is tung oil.

3. The process of claim 2 wherein is admixed with said tung oil.

4. The process of claim 1 air.

5. The process of claim 1 wherein said oxidizable liquid is linseed oil.

6. The process of claim 1 wherein air is the oxidant, tung oil is the oxidizable liquid, and a minor but effective amount of an oxidation catalyst is admixed with the tung oil.

7. The process of claim 6 prises cobalt naphthenate.

8. The process of claim 1 wherein air is the oxidant and air is injected thru said central Well prior to Step 1 until air breaks thru into said first and second wells.

9. The process of claim 1 including the steps of:

(7) prior to Step 1, passing a solvent for the in-place oil thru the annulus surrounding said central well; and

(8) displacing solvent and any dissolved oil therein from said annulus by Step 1.

an oxidation catalyst wherein said oxidant is wherein said catalyst com- References Cited UNITED STATES PATENTS 2,793,697 5/1957 Simm et al. 16639 2,863,510 12/1958 Tadema et al. 166-38 3,179,169 4/1965 Cline et al. 16638 3,180,412 4/1965 Bednarski et a1 166-11 3,314,476 4/ 1967 Staples et al 16639 X 3,324,945 6/1967 Lumpkin et a1. 16611 STEPHEN I. NOVOSAD, Primary Examiner. 

1. A PROCESS FOR INITIATING IN SITU COMBUSTION IN A PERMEABLE OIL STRATUM PENETRATED BY A CENTRAL WELL AND FIRST AND SECOND WELLS OFFSET IN SUBSTANTIALLY OPPOSITE DIRECTIONS FROM SAID CENTRAL WELL, WHICH COMPRISES THE STEPS OF: (1) INJECTING THRU SAID CENTRAL WELL A COMBUSTIONSUPPORTING VOLUME OF A LOW-TEMPERATURE OXIDIZABLE LIQUID INTO AN ANNULUS OF SAID STRATUM ADJACENT SAID CENTRAL WELL; (2) THEREAFTER, SHUTTING IN SAID CENTRAL WELL AND INJECTING GASEOUS O2-CONTAINING OXIDANT THRU SAID FIRST WELL SO AS TO CONTACT SAID LIQUID THEREWITH AND IGNITE AND BURN SAME, THEREBY IGNITING IN-PLACE OIL ADJACENT SAID ANNULUS AND ESTABLISHING A COMBUSTION ZONE; (3) CONTINUING THE INJECTING IN STEP 2 SO AS TO CAUSE SAID COMBUSTION ZONE TO MOVE TOWARD SAID FIRST WELL (4) DURING STEPS 2 AND 3, PRODUCING THRU SAID SECOND WELL; (5) THEREAFTER, OPENING SAID CENTRAL WELL TO PRODUCTION AND INJECTING GASEOUS O2-CONTAINING OXIDANT THRU SAID SECOND WELL, CONTACTING THE OXIDIZABLE LIQUID IN SAID ANNULUS NEAREST SAID SECOND WELL THEREWITH, AND BURNING SAID LIQUID THEREBY IGNITING IN-PLACE OIL AND ESTABLISHING A SECOND COMBUSTION ZONE; AND (6) CONTINUING THE INJECTING IN STEP 5 SO AS TO MOVE SAID SECOND COMBUSTION ZONE TOWARD SAID SECOND WELL WHILE PRODUCING FLUIDS FROM BOTH COMBUSTION ZONES THRU SAID CENTRAL WELL. 